Rare condors harmed by DDT in food chain, study discovers

Email Newsletters

Daily Photo Galleries

Traveling by Jeep, boat and foot, Tribune-Review investigative reporter Carl Prine and photojournalist Justin Merriman covered nearly 2,000 miles over two months along the border with Mexico to report on coyotes — the human traffickers who bring illegal immigrants into the United States. Most are Americans working for money and/or drugs. This series reports how their operations have a major impact on life for residents and the environment along the border — and beyond.

By The Associated Press

Sunday, Sept. 15, 2013, 5:39 p.m.

SAN FRANCISCO — In the coastal redwood forests of central California, scientists trying to unravel the mystery surrounding the reproductive problems of dozens of endangered condors think they have uncovered the culprit: the long-banned pesticide DDT.

The soaring scavengers with wingspans wider than NBA players are tall were reintroduced to the rugged coast of Big Sur in 1997 after a century-long absence. Upon arrival, the birds found plenty to eat, with dead California sea lions and other marine mammals littering the craggy shoreline.

While a good food source, sea lion blubber often has high levels of DDT, a pesticide banned in 1972 that has proved to be a persistent pollutant because it accumulates in bodies of creatures throughout the food chain when animals eat one another.

Once used widely in agriculture, DDT was banned because it is a human toxin considered a possible carcinogen by the Centers for Disease Control and Prevention.

Kelly Sorenson, executive director of Ventana Wildlife Society and a co-author of a new study on condors, said researchers who spent six years studying their reproductive problems have “established a strong link” to DDT in the birds' food source.

The peer-reviewed paper written by 10 condor experts, including biologists from the Los Angeles and Santa Barbara zoos and the Fish and Wildlife Service, is being published this month in the University of California journal The Condor.

“In science, rarely is anything definitive, but we've established a strong link between ... DDT and eggshell thinning in California condors,” Sorenson told The Associated Press.

The eggshell mystery began in 2006, when a biologist inspecting a condor nest in the cavity of a redwood tree on the central California coast found the first thin shell.

Over the next six years, the scientists observed condors feeding on dozens of sea lions, and found that the Big Sur condor population had a low hatching success — just 20-40 percent — for 16 nesting pairs. In contrast, 70 to 80 percent of southern California condors in the Tejon area had hatched successfully over the same time. The southern California condors are inland, and sea lions are not a food source.

Biologists familiar with the ravages of DDT in bird populations immediately suspected the widely used pesticide as a factor.

Tests since the 1970s have found high levels of DDT in sea lions; and studies have linked DDT's metabolized version, DDE, to egg shell thinning in birds, including brown pelicans and bald eagles.

TribLive commenting policy

You are solely responsible for your comments and by using TribLive.com you agree to our Terms of Service.

We moderate comments. Our goal is to provide substantive commentary for a general readership. By screening submissions, we provide a space where readers can share intelligent and informed commentary that enhances the quality of our news and information.

While most comments will be posted if they are on-topic and not abusive, moderating decisions are subjective. We will make them as carefully and consistently as we can. Because of the volume of reader comments, we cannot review individual moderation decisions with readers.

We value thoughtful comments representing a range of views that make their point quickly and politely. We make an effort to protect discussions from repeated comments  either by the same reader or different readers.

We follow the same standards for taste as the daily newspaper. A few things we won't tolerate: personal attacks, obscenity, vulgarity, profanity (including expletives and letters followed by dashes), commercial promotion, impersonations, incoherence, proselytizing and SHOUTING. Don't include URLs to Web sites.

We do not edit comments. They are either approved or deleted. We reserve the right to edit a comment that is quoted or excerpted in an article. In this case, we may fix spelling and punctuation.

We welcome strong opinions and criticism of our work, but we don't want comments to become bogged down with discussions of our policies and we will moderate accordingly.

We appreciate it when readers and people quoted in articles or blog posts point out errors of fact or emphasis and will investigate all assertions. But these suggestions should be sent via e-mail. To avoid distracting other readers, we won't publish comments that suggest a correction. Instead, corrections will be made in a blog post or in an article.

Total Promotional Solutions

A division of Trib Total Media is your one-stop-shop for all of your branded merchandise needs.

We specialize in providing quality affordable promotional products for every type of business including non-profits, schools, universities, sports teams and more. With 1000’s of products to choose from, our knowledgeable staff can help you find the perfect apparel item or product to suit your needs and budget.

Digital Sales

We offer a wide variety of traditional and new digital advertising options customized to fit your needs!

Whether you're just starting out, or you've been a keystone in the community for years, our knowledgeable staff can provide you with a customized package including online banners/advertisements, Social Media Marketing (Facebook / Twitter), Website development, Search Engine Optimization, Email Marketing solutions and much more!

Contact your local sales rep today for details, personalized proposal and a meeting to discuss how we can meet your needs.